[1] Univ Calif San Diego, San Diego Med Ctr, Dept Radiol, Sch Med, San Diego, CA 92103 USA
[2] Univ Manitoba, Dept Med, Winnipeg, MB R3T 2N2, Canada
[3] St Boniface Gen Hosp, Sleep Disorders Ctr, Winnipeg, MB R2H 2A6, Canada
[4] Univ Calif San Diego, Sch Med, Dept Family & Prevent Med, San Diego, CA 92103 USA
[5] San Diego State Univ, Grad Sch Publ Hlth, San Diego, CA 92182 USA
[6] Univ Western Ontario, Dept Med, London, ON N6A 3K7, Canada
[7] VA San Diego Hlth Syst, San Diego, CA USA